A polyalkylene terephthalate resin such as a polybutylene terephthalate has excellent mechanical and electrical properties, weather resistance, water resistance, and resistance to chemicals and solvents. Such a resin is, therefore, used as an engineering plastic in various purposes such as electric or electronic device parts, mechanical device parts and automotive parts. While, the resin is required to be flame-retardant from viewpoint of safety as the field of their uses expands. In general, there is known a method for rendering a resin flame-retardant by adding a halogen-series flame retardant composed of a halogen-series (halogen-containing) compound or a halogen-series compound in combination with an antimony-series (antimony-containing) compound to the resin. However, the halogen-series flame retardant is not preferable for environmental reasons because the flame retardant sometimes generates a large amount of a dioxin-series compound on resolution caused by combustion. Therefore, there is proposed a method for rendering the polyester-series resin flame-retardant by using a phosphorus-series (phosphorus-containing) compound as a halogen-free flame retardant.
Japanese Patent Application Laid-Open No. 168297/1998 (JP-10-168297A) discloses a flame-retardant resin composition comprising a thermoplastic polyester resin, a polycarbonate-series resin, and an organic phosphorus-series (phosphate-series) flame retardant. Japanese Patent Application Laid-Open No. 195283/1998 (JP-10-195283A) discloses a polyester resin composition to which flame retardancy is imparted with the combination use of a phosphoric ester having a specific structure, a novolak-based phenol resin, and an oxide of a specific metal (such as iron, cobalt, nickel or copper) in an adequate amount. Japanese Patent Application Laid-Open No. 212412/2000 (JP-2000-212412A) discloses a flame retardant resin composition comprising a thermoplastic polyester resin, a vinyl-series resin, an organic phosphorus-series flame retardant (such as a condensed phosphoric ester) and a glass fiber. The phosphoric ester-series flame retardant does not comprise harmful halogens; however, the flame retardant is inferior to a halogen-series flame retardant in flame retardancy, so that it is necessary to add a large amount of the flame-retardant. The addition of a large amount of the flame-retardant brings about bleeding out (blooming) and deteriorating in mechanical properties of a resin. It is, therefore, impossible to improve both flame retardancy, and mechanical properties.
Moreover, Japanese Patent Application Laid-Open No. 181268/1999 (JP-11-181268A) discloses that addition of 1.5 to 15 parts by weight of a phosphazene compound and 0.5 to 30 parts by weight of a talc and/or mica to 100 part by weight of a resin mixture containing an aromatic polycarbonate-series resin and a thermoplastic polyester-series resin in a ratio (weight ratio) of 90/10 to 50/50 [the former/the latter] can impart flame retardancy to the resin mixture. However, such an aromatic polycarbonate-based resin composition has a problem in resistance to solvents. In addition, melt-flowability of the resin composition is deteriorated upon a molding process, and moldability (formability) thereof is adversely affected.
Incidentally, Japanese Patent Application Laid-Open No. 181429/1999 (JP-11-181429A) discloses impartment of flame retardancy to either a thermoplastic resin (such as a polyethylene terephthalate, a polybutylene terephthalate and a polycarbonate) or a thermosetting resin (such as a phenolic resin) by using a specific phosphazene compound (e.g., a cyclic phosphazene compound, a linear phosphazene compound, a crosslinked phosphazene compound formed by crosslinking the cyclic and/or the linear phosphazene compound(s) with a specific group) as a flame retardant. However, in the case where flame retardancy is imparted to a polyethylene terephthalate or a polybutylene terephthalate, satisfactory flame retardancy cannot be imparted thereto with the phosphazene compound alone.
It is therefore an object of the present invention to provide a flame-retardant resin composition being rendered flame-retardant to a high level without deteriorating properties of a polyalkylene arylate-series resin, and a process for producing the same.
It is another object of the invention to provide a flame-retardant resin composition in which bleeding out of a flame retardant is inhibited, no metal corrosion occurs, and moldability is excellent, and to which high flame-retardancy is imparted, as well as a shaped (or molded) article formed with the composition.